Process for preparation of dibenzocyclooctadiene type lignan

ABSTRACT

A dibenzocyclooctadiene type lignan can be efficiently prepared by extracting a plant containing a dibenzocyclooctadiene type lignan with a low polar solvent, subjecting the resulting extract to partition extraction with a water-insoluble low polar solvent and a water-soluble high polar solvent, at least one time, and recovering the dibenzocyclooctadiene type lignan from the layer of the water-soluble high polar solvent.

DESCRIPTION

1. Technical Field

The present invention relates to a process for the preparation ofdibenzocyclooctadiene type lignan which is valuable as a medicine.

2. Background Art

It is generally known that many dibenzocyclooctadiene type lignans areeffective as medicines. For example, it is known that schizandrincomprises analgesic action, gomisin A and gomisin C comprise livertrouble-moderating action, and deoxyschizandrin exhibits anti-ulceraction.

It is known in the art to obtain dibenzocyclooctadiene type lignans fromplants to treat plant extracts containing said lignans to chromatographyusing as the adsorbent, for example, silica gel, ODS silica gel,alumina, Celite or a porous polymer gel such as Dia-Ion HP-20 repeatedlyto effect purification. But the process comprising subjecting a plantextract containing large quantities of impurities directly to thechromatography is defective as an industrial preparation process becausea large quantity of the adsorbent must be used, the deterioration speedof the adsorbent is high, and a large quantity of the solvent must beused for the chromatography. To use a specific dibenzocyclooctadienetype lignan as a medicine, it is necessary to prepare this lignan in alarge quantity, and therefore, a simple process capable of providing anintended lignan in a large quantity is desired.

Disclosure of the Invention

The inventors carried out research with a view to developing a processcapable of providing a large quantity of a dibenzocyclooctadiene typelignan by simple means, and as a result, found that, if the partitionextraction method is adopted, the amounts of the adsorbent and solventused for the chromatography can be greatly reduced and an intendeddibenzocyclooctadiene type lignan can be very simply prepared in a largequantity. The present invention is based on this finding.

More specifically, in accordance with the present invention, there isprovided a process for the preparation of a dibenzocyclooctadiene typelignan, which comprises extracting a plant containing adibenzocyclooctadiene type lignan with a low polar solvent, subjectingthe resulting extract to the partition extraction using awater-insoluble low polar solvent and a water-soluble high polar solventat least one time, and recovering the dibenzocyclooctadiene type lignanfrom the layer of the water-soluble high polar solvent.

Best Mode of Carrying Out the Invention

As the dibenzocyclooctadiene type lignan-containing plant to beextracted in the present invention, there can be mentioned plantsbelonging to the family Schisandraceae, such as Schisandra chinensisBaill., Schisandra sphenathera Rehd. et Wils., Schisandra rubriflola andKadsura japonica.

As specific examples of the low polar solvent valuably used in thepresent invention, there can be mentioned petroleum ether, n-hexane,n-heptane, benzene, toluene and cyclohexane. The extraction is carriedout at a temperature in the range of from room temperature to theboiling point of the used solvent, preferably under heating.

Then, the extract is subjected to the partition extraction (hereinafterreferred to as "partition") using a water-insoluble low polar solventand a water-soluble high polar solvent. If the solvent used for thepartition is the same as the solvent used for the extraction, thenpreferably the partition is carried out after the extract has beencondensed at an appropriate concentration or dried. If the solvent usedfor the partition is different from the solvent used for the extraction,preferably the partition is carried out after the extract has beendried.

As specific examples of the low-polarity water-insoluble solvent, therecan be mentioned petroleum ether, n-hexane, n-heptane, benzene, tolueneand cyclohexane, and as the high-polarity water-soluble solvent, therecan be mentioned methanol and ethanol. The proportion of thehigh-polarity water-soluble solvent in the solvent is preferably from 40to 80%, most preferably from 55 to 65%. The partition can be performedby customary procedures.

The partition can be accomplished more efficiently if a salt is added.As the salt sodium chloride, potassium chloride, ammonium sulfate andsodium sulfate can be used. When a salt is added, a partition withchloroform or the like is preferably carried out, to remove the saltfrom the high-polarity water-soluble solvent.

After the above-mentioned partition operation, to obtain the intendeddibenzocyclooctadiene type lignan from the high-polarity water-solublesolvent layer, such means as concentration, drying, filtration,recrystallization, column chromatography, and high-speed liquidchromatography can be adopted. Recrystallization can be carried outaccording to customary procedures by using a solvent selected fromwater, petroleum ether, n-hexane, n-heptane, benzene, toluene,cyclohexane, chloroform, methylene chloride, ether, tetrahydrofuran,ethyl acetate, acetone, ethanol, methanol and isopropanol, or two ormore mixed solvent of above solvents. When column chromatography iscarried out by using an adsorbent such as silica gel, ODS silica gel,alumina or a porous polymer gel, single or mixed solvent selected frompetroleum ether, n-hexane, benzene, toluene, chloroform, methylenechloride, ether, ethyl acetate, acetone, ethanol, methanol and water canbe used as the solvent.

When high-speed liquid chromatography is carried out, a commerciallyavailable column of the normal phase or reversed phase can be used, andan organic solvent suitable for the column used can be used as themoving phase.

The foregoing operations can be carried out in combination, according toneed.

As specific examples of the dibenzocyclooctadiene type lignan obtainedaccording to the above-mentioned procedures, gomisin A, schizandrin,deoxyschizandrin and gomisin C can be mentioned.

The present invention will now be described in detail with reference tothe following examples, that by no means limit the scope of theinvention.

EXAMPLE 1

Schisandra chinensis Baill. (10 kg) was refluxed and extracted for 1.5hours with 50 l of hexane, the extract was dried under a reducedpressure to obtain 978.8 g of a hexane extract, the hexane extractdissolved in 9.8 l of hexane, and then extracted two times with 9.8 l of60% (v/v) methanol. Two extracts (lower layers) were combined, and themixture was dried under a reduced pressure to obtain 112.2 g of afraction having a high lignan content.

The above-mentioned fraction having a high lignan content was subjectedto the fractionation high-speed liquid chromatography [column: KieselGel 60 (230 to 400 mesh) supplied by Merk, diameter=10 cm, length=100cm, moving phase: n-hexane/ethyl acetate (7/3), flow rate: 200 ml/min,apparatus: Waters Prep LC/System 500A]. Fractions eluted at 123 to 133minutes were combined and dried under a reduced pressure, and theresidue was recrystallized from methanol to obtain 11.66 g of acolorless needle crystal. The physical and chemical properties of thiscolorless needle crystal were in agreement with those of gomisin Adescribed in the literature reference [H. Taguchi and Y. Ikeya, Chem.Pharm. Bull., 23(12), 3296 (1975)].

EXAMPLE 2

Fractions eluted at 140 to 170 minutes in the fractionation high-speedliquid chromatography conducted in Example 1 were combined and driedunder a reduced pressure. The obtained residue was recrystallized from amixed solvent of ether and n-hexane to obtain 950 mg of a colorlessprism crystal. The physical and chemical properties of this colorlessprism crystal were in agreement with those of Schizandrin disclosed inthe literature reference [Y. Ikeya, H. Taguchi, I. Yoshioka and H.Kobayashi, Chem. Pharm. Bull., 27(6), 1383(1979)].

EXAMPLE 3

Fractions eluted at 63 to 70 minutes in the fractionation high-speedliquid chromatography conducted in Example 1 were combined and driedunder a reduced pressure, and the obtained residue was recrystallizedfrom methanol to obtain 1.05 g of a colorless prism crystal. Thephysical and chemical properties of the obtained colorless prism crystalwere in agreement with those of deoxyschizandrin disclosed in theliterature reference [N. K. Kochetkov, A. Khorlin and O. S. Chizov,Tetrahedron Letters, 1962, 361].

EXAMPLE 4

Schisandra chinensis Baill. (1 kg) was refluxed and extracted for 2hours with 5 l of hexane, and the extract was dried and 99.5 g of theobtained hexane extract was dissolved in 1 l of n-hexane and extractedtwo times with 1 l of 50% (v/v) of methanol. The two extracts (lowerlayers) were combined and lignans were extracted with chloroform, thechloroform extract was washed with water and dried under a reducedpressure, and 12.40 g of the obtained residue was subjected to thecolumn chromatography using 200 g of silica gel (Kiesel Gel 60 suppliedby Merk, 70 to 230 mesh). After elution with 1 l of n-hexane/ethylacetate (85/15), elution was carried out with 2 l of n-hexane/ethylacetate (3/1). Fractions eluted with n-hexane/ethyl acetate (3/1) werecombined and dried under a reduced pressure, and the residue wasrecrystallized from methanol to obtain 669 mg of gomisin A in the formof a colorless needle crystal.

EXAMPLE 5

In 1 l of n-hexane 99.5 g of the n-hexane extract obtained in Example 4was dissolved, and the solution was extracted with 1 l of sodiumchloride-saturated 60% (v/v) methanol two times. The two extracts (lowerlayers) were combined, and lignans were extracted with 1 l ofchloroform. The chloroform extract was washed with water and dried undera reduced pressure, and 12.61 g of the obtained residue wasrecrystallized from methanol to obtain 483 mg of Gomisin A in the formof a colorless needless crystal.

EXAMPLE 6

The chloroform extract (12.40 g) obtained in Example 4 was subjected tothe column chromatography using ODS silica gel [column: YMC Gel ODS1-25/45, diameter=3 cm, length=50 cm, moving phase: methanol/water(7/3), flow rate: 6 ml/min]. The eluate obtained at 50 to 110 minuteswas dried under reduced pressure and the residue was recrystallized fromether/n-hexane to obtain 1.35 g of Schizandrin in the form of acolorless prism crystal. Furthermore, the fraction eluted at 150 to 200minutes was dried under a reduced pressure, and the obtained residue wasrecrystallized from methanol to give 1.26 g of gomisin A as a colorlessneedle crystal.

EXAMPLE 7

In 1 l of n-hexane 99.5 g of the n-hexane extract obtained in Example 4was dissolved, and the solution was extracted with 1 l of sodiumchloride-saturated 65% (v/v) methanol two times. The two extracts (lowerlayers) were combined, and lignans were extracted with 1 l ofchloroform. The chloroform extract was washed with water and dried undera reduced pressure, and 12.53 g of the obtained residue wasrecrystallized from methanol to obtain 467 mg of gomisin A as acolorless needle crystal.

EXAMPLE 8

In 1 l of n-hexane 99.5 g of the n-hexane extract obtained in Example 4was dissolved, and the solution was extracted with 1 l of sodiumchloride-saturated 70% (v/v) methanol two times. The two extracts (lowerlayers) were combined and lignans were extracted with 1 l of chloroformtwo times. The chloroform extracts were combined, washed with water anddried under a reduced pressure, and 14.01 g of the obtained residue wasrecrystallized from methanol to obtain 422 mg of Gomisin A as acolorless needle crystal.

EXAMPLE 9

Schisandra chinensis Baill. (300 g) was refluxed and extracted for 3hours with 3 l of petroleum ether, and the extract was dried under areduced pressure and 28.7 g of the petroleum ether extract was dissolvedin 280 mg of petroleum ether. The solution was extracted with 280 ml ofammonium sulfate-containing 60% (v/v) methanol two times. The twoextracts were combined and lignans were extracted with 280 ml ofchloroform. The chloroform extract was washed with water and dried undera reduced pressure and 4.68 g of the obtained residue was subjected tothe column chromatography using 80 g of silica gel (Kiesel Gel 60supplied by Merk, 230 to 400 mesh). After elution with 0.6 l ofn-hexane/ethyl acetate (4/1), elution was carried out with 0.3 l ofn-hexane/ethyl acetate (7/3). The n-hexane/ethyl acetate (7/3) eluatewas dried under reduced pressure and 967 mg of the residue wasrecrystallized from methanol to give 305 mg of gomisin A as a colorlessneedle crystal.

EXAMPLE 10

Schisandra sphenanthera Rehd. et Wils. (435 g) was refluxed andextracted for 3 hours with 2 l of n-hexane two times. The extract wasdried under a reduced pressure to obtain 43.40 g of an n-hexane extract.The n-hexane extract was dissolved in 430 ml of n-hexane, and partitionextraction was carried out with 430 ml of sodium chloride-saturated 60%(v/v) methanol two times. The two extracts (lower layers) were combinedand lignans were extracted with 430 ml of chloroform. The chloroformextract was washed with water and dried under a reduced pressure toobtain 6.84 g of a fraction having a high lignan content. This fractionhaving a high lignan content was subjected to the column chromatography(diameter=5 cm, length=15 cm) using silica gel (Kiesel 60 supplied byMerk, 230 to 400 mesh), and elution was carried out with a mixed solventof n-hexane and ethyl acetate. Namely, 400 ml of n-hexane/ethyl acetate(7/3), 200 ml of n-hexane/ethyl acetate (6/4) and then, 200 ml ofn-hexane/ethyl acetate (1/1). The n-hexane/ethyl acetate (1/1) eluatewas dried under a reduced pressure and the residue was recrystallizedfrom methanol to give 430 mg of a colorless prism crystal. The physicaland chemical properties of this colorless prism crystal were inagreement with those of gomisin C disclosed in the literature reference[H. Taguchi and Y. Ikeya, Chem. Pharm. Bull., 23(12), 3296 (1975)].

Industrial Applicability

The present invention can be advantageously utilized for the productionof dibenzocyclooctadiene type lignans valuable as medicines.

We claim:
 1. A process for the preparation of a dibenzocyclooctadienetype lignan, which comprises extracting a plant containing adibenzocyclooctadiene type lignan with a low polar solvent selected fromthe group consisting of petroleum ether, n-hexane, n-heptane, benzene,toluene and cyclohexane, subjecting the resulting extract to at leastone partition extraction with a water-insoluble low polar solventselected from the group consisting of petroleum ether, n-hexane,n-heptane, benzene, toluene and cyclohexane, and a water-soluble highpolar solvent selected from the group consisting of methanol andethanol, and recovering the dibenzocyclooctadiene type lignan from thelayer of the water-soluble high polar solvent.
 2. A process according toclaim 1, wherein the plant containing a dibenzocyclooctadiene typelignan is selected from the group consisting of Schisandra chinensisBaill., Schisandra sphenathera Rehd. et Wils. Schisandra rubriflola andKadsura japonica.
 3. A process according to claim 1, wherein the samelow polar solvent is used during the initial extraction and thepartition extraction, and the partition extraction is carried out afterthe extract has been condensed or dried.
 4. A process according to claim1, wherein a different polar solvent is used during the initialextraction than is used during the partition extraction, and thepartition extraction is carried out after the extract has been dried. 5.A process according to claim 1, wherein the proportion of thewater-soluble high polar solvent in the solvent used for the partitionextraction is 40 to 80%.
 6. A process according to claim 5, wherein saidproportion is 55 to 65%.
 7. A process according to claim 1, wherein thepartition extraction is carried out in the presence of a salt.
 8. Aprocess according to claim 7, wherein the salt is selected from thegroup consisting of sodium chloride, potassium chloride, ammoniumsulfate and sodium sulfate.
 9. A process according to claim 1, whereinthe dibenzocyclooctadiene type lignan is recovered by concentration,drying filtration, recrystallization, column chromatography orhigh-speed liquid chromatography.
 10. A process according to claim 1,wherein the obtained dibenzocyclooctadiene type lignan is selected fromthe group consisting of gomisin A, schizandrin, deoxyshizandrin andgomisin C.